describe the habit,habitat and morphology of mass
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Answer:
this article we will discuss about:- 1. Habit and Habitat of Lycopodium 2. External Morphology of Lycopodium 3. Internal Structure 4. Reproduction 5. Morphological Nature of Protocorm 6. Economic Importance 7. Life Cycle Patterns.
Habit and Habitat of Lycopodium:
Lycopodium is commonly known as ‘club moss’ due to their moss like appearance and club shaped strobili. It has about 400 species, which are cosmopolitan in distribution. They are found in colder arctic region as well as in temperate, tropical and sub-tropical regions but they are abundantly found in tropical zones.
Thirty three species of Lycopodium have been reported from India. Mostly it is found growing in moist and shady places which are rich in humus and other organic matters. Some of the common species are L. clavatum, L. phlegmaria, L. cernuum, etc.
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It has got 2 sub-genuses:
(i) Urostachya—branching dichotomous and roots originate from the base of the stem.
(ii) Rhopalostachya—stem prostrate with erect branching and roots arise adventitiously from all along the stem.
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Mostly the tropical species are epiphytic (e.g., L. phlegmaria) and grow hanging from the tree trunks. The temperate species may be erect and shruby (e.g., L. reflexum), creeping (e.g., L clavatum) or erect form (e.g., L. cernuum) etc.
External Morphology of Lycopodium:
The herbaceous plant body is sporophytic. Usually they may have either prostrate stem with erect leafy branches or weak pendent stem (epiphytes).
The plant body is distinctly differentiated into following three regions (Fig. 1 A-C):
(i) Stem,
(ii) Roots, and
(iii) Leaves.
(i) Stem:
In the sub-genus Urostachya stem is erect (terrestrial) or pendent (epiphytic) and may be branched (dichotomously) or unbranched. In the sub-genus Rhopalostachya the stem is prostrate with erect branches. First the branching is dichotomous and later on becomes monopodial.
(ii) Root:
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Usually small, adventitious roots are present. In the sub-genus Urostachya roots originate only from the base of the stem (not arising from the whole length of the stem). In some species e.g., L. selago etc. the roots arise endogenously from pericycle of the stem, do not penetrate the cortex of the stem but turn downward through the cortex and finally emerge only at the base of the stem.
Due to this reason a T. S. of stem usually shows roots within the cortex and are known as cortical roots (inner roots). In sub-genus Rhopalostachya also roots are adventitious and arise all along the underside of the prostrate portion of the stem.
(iii) Leaves:
Leaves are simple, sessile, small in size, eligulate and possess a single unbranched midrib and are known as microphylls. Usually the leaves are spirally arranged (e.g., L. clavatum) but may be arranged in whorls (e.g., L. cernuum) or pairs (e.g., L. alpinum).
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In all the cases they condensely cover the surface of the stem. Leaves are usually homophyllous (isophyllous) i.e., of same size and shape but in some cases e.g., in L. complanatum the leaves are heterophyllous (anisophyllous) i.e., of different size.
Usually the leaves near the apical portion of the branches bear sporangia and are called sporophylls. Depending upon the species the sporophylls may or may not be differentiated from the ordinary leaves.
These sporophylls usually form a condense structure at the apex of the branches which are known as strobili. The numbers of strobili at the tip of branches differ in different species.
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Internal Structure of Lycopodium:
(a) Stem:
A transverse section (T.S.) of the stem of Lycopodium is somewhat circular in outline and can be differentiated into following three regions:
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1. Epidermis:
It is the outermost covering layer comprising of single cell in thickness. The epidermis is cutinised on the outer side and interrupted at places by the presence of stomata.
2. Cortex:
Inner to the epidermis is present a wide zone of cortex which shows a great variation in its structure in di